A South Sudanese woman at a refugee camp. Photograph: Tony Karumba/AFP/Getty Images

The father of South Sudanese resistance, the late Dr John Garang, never quite ruled out the possibility of seceding from the north to create a new, independent state. But nor did he advocate it. For him, secession was a last resort, an option to be taken only if everything else had failed. "If we cannot rise to the challenge and move to the New Sudan, it is better that the Sudan breaks up before it breaks down," he said in speeches delivered across the continent and the world.

But his vision, his dream, was always to meet that challenge; to make a New Sudan which could accommodate its wonderfully diverse peoples, and give them all a say in the running of the state. In January 2005, at the signing ceremony of the Comprehensive Peace Agreement in Nairobi – the deal which ended the decades-long civil war between the Sudanese government and the SPLM/A rebels of which Garang was chief – he reiterated this to the 20,000 Sudanese and the 15 African heads of state who were assembled for the occasion: "This peace agreement signals the beginning of one Sudan regardless of race, religion or tribe."

Six months later, his helicopter crashed in circumstances which continue to fuel conspiracy theories. Garang was dead, and with him and with him any hope of a unified Sudan.

Garang's vision was never particularly popular amongst his people, and understandably so. Secession seemed like (and ultimately was) an achievable goal, whereas overthrowing Sudanese President Omar al-Bashir and his henchmen was an exponentially more difficult challenge; and after enduring centuries of oppression from northern rulers, southerners were entitled to feel aggrieved enough to want to cut ties completely.

South Sudanese soldiers on their vehicle patrol a street in Juba, South Sudan. Photograph: Phillip Dhil/EPA

Even within his own party, Garang had to push hard for unity. Without the force of his personality – and under the guidance of his deputy, Salva Kiir, a committed secessionist – impetus swung swiftly and irreversibly the other way. The international community, led by activists from the United States, pushed hard in the same direction.

Sure enough, by the time the referendum came around in 2011, South Sudanese voted overwhelmingly to create a new, independent state. South Sudan was born.

Just two and a half short years later, the world's newest state is on the brink of collapse. Kiir's army, the only functional institution, is divided between his supporters and those of Vice-President Riek Machar. Fighting in the capital Juba and other areas has taken on dangerous ethnic overtones. Thousands are dead, tens of thousands have fled the country and hundreds thousands more are displaced within South Sudan's borders.

"Even before the recent fighting broke out in December, 80% of healthcare and basic services in South Sudan were provided by non-governmental organisations," observed Doctors Without Borders (MSF), in their latest, urgent missive. Now many of those NGOs are gone (MSF being a notable exception), and the situation is rapidly deteriorating. "What was already a difficult situation has become even worse."

Oil, the country's only asset of note, has stopped flowing completely; so completely that even the Chinese, notoriously reluctant to intervene in the internal affairs of African nations, have issued a stern rebuke, mindful of their significant energy interests in the country.

In short, the South Sudanese state – barely there to begin with – has already failed.

It's worth pondering, at this juncture of South Sudan's history, if perhaps John Garang was right – and southern Sudanese, not to mention northerners who have continued living under oppression, would have been better served by trying to reform Sudan in its entirety?

South Sudanese civilians crowd at the United Nations mission in Bor. Photograph: Handout/Reuters

South Sudan, on its own, doesn't have much going for it. "The new state was born with all the makings of a crisis," argues William Wallis in the Financial Times. "Its development had been stunted by five decades of intermittent war. Unlike other African liberation movements, the now fractured Sudan People's Liberation Movement had few if any social programmes in areas it controlled. There were few functioning institutions beyond the army and less infrastructure than most African nations had when colonial powers began to withdraw."

This underdevelopment is further entrenched by a few geographical and infrastructural realities. It's a landlocked country, which means it can't ship any of its abundant oil to buyers. For that, the oil must travel via pipeline through Sudan proper, to the tankers waiting at Port Sudan. Or it must go by truck on dodgy roads to neighbours Ethiopia, Kenya and Uganda, because a pipeline heading south hasn't been built yet (and won't for some time to come). Many places in the country aren't connected by road, and are completely cut off during the rainy season (some of refugee camps, for example, are only accessible via helicopter).

Besides oil, the country has almost no industry to speak of. While there's potential for agriculture – South Sudanese officials keep talking about turning the country into the "breadbasket of east Africa" – it's a long way from happening, and the biggest factory in Juba is the local brewery (run by SABMiller).

Post-secession Sudan, meanwhile, is also in trouble. Its economy has been devastated by the sudden cut-off in oil funds, which for so long were used to keep the population complacent and compensate for the economic impact of the sanctions (these were levied against Khartoum for its role in Darfur).

A united Sudan, meanwhile, without sanctions, with a reliable oil income that is properly invested in national infrastructure, healthcare and education programs, has the potential to be more than the current sum of its parts – the strengths of the north complementing those of the south, and vice versa. This may be little more than a mirage, but it's an alluring prospect nonetheless, and one for which John Garang was prepared to fight, and even sacrifice the prospect of immediate power. His successors, possessed of shorter-term vision, settled for the easy money compromise – a lack of foresight for which South Sudan might just be paying the price.

• This article was amended on 12 January 2014 to reflect that South Sudan became independent two-and-a-half years ago, not three-and-a-half, as originally stated.